US4243327A
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US
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Double-beam optical method and apparatus for measuring thermal diffusivity and other molecular dynamic processes in utilizing the transient thermal lens effect
Assignee: National Aeronautics and Space Administration
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Filing: 1979-01-31
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Granted: 1981-01-06
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Expires: 1999-01-31
Abstract
Abstract A method and apparatus for measuring thermal diffusivity and molecular relaxation processes in a sample material utilizing two light beams, one being a pulsed laser light beam for forming a thermal lens in the sample material, and the other being a relatively low power probe light beam for measuring changes in the refractive index of the sample material during formation and dissipation of the thermal lens. More specifically, a sample material is irradiated by relatively high power, short pulses from a dye laser. Energy from the pulses is absorbed by the sample material, thereby forming a thermal lens in the area of absorption. The pulse repetition rate is chosen so that the thermal lens is substantially dissipated by the time the next pulse reaches the sample material. A probe light beam, which in a specific embodiment is a relatively low power, continuous wave (cw) laser beam, irradiates the thermal lens formed in the sample material. The intensity characteristics of the probe light beam subsequent to irradiation of the thermal lens is related to changes in the refractive index of the sample material as the thermal lens is formed and dissipated. A plot of the changes in refractive index as a function of time during formation of the thermal lens as reflected by changes in intensity of the probe beam, provides a curve related to molecular relaxation characteristics of the material, and a plot during dissipation of the thermal lens provides a curve related to the thermal diffusivity of the sample material.
Inventors
- 👤 with respect to an invention of Frosch Robert A. Administrator of the National Aeronautics and Space Administration
- 👤 Jovan Moacanin
- 👤 Amitava Gupta
- 👤 Su-don Hong
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:25
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/171; G01N25/00; G01N25/18; G01N2021/1712
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
178 words
An apparatus for measuring thermal diffusivity of a sample material comprising: a pulsed laser light source for providing a pulsed laser light beam directed to irradiate said sample material whose thermal diffusivity is to be measured, said pulsed laser light beam characteristics being chosen to cause formation of a thermal lens in said sample material; a probe light beam source for providing a probe light beam directed to irradiate said thermal lens; a probe light beam focusing lens located between said probe light beam source and said sample material, said focusing lens providing a converging/diverging beam with a focal point at a predetermined location with respect to said thermal lens thereby resulting in an intensity alteration of said probe light beam as a result of irradiating said thermal lens; and means for detecting the intensity of at least a portion of said probe light beam after having irradiated said thermal lens during a portion of the dissipation time of said thermal lens, thereby providing an intensity versus time profile related to the thermal diffusivity of said sample material.
Claim 2
Independent Claim
178 words
An apparatus for measuring thermal diffusivity of a sample material comprising: a pulsed laser light source for providing a pulsed laser light beam directed to irradiate said sample material whose thermal diffusivity is to be measured, said pulsed laser light beam characteristics being chosen to cause formation of a thermal lens in said sample material; a probe light beam source for providing a probe light beam directed to irradiate said thermal lens; a probe light beam focusing lens located between said probe light beam source and said sample material, said focusing lens providing a converging/diverging beam with a focal point at a predetermined location with respect to said thermal lens thereby resulting in an intensity alteration of said probe light beam as a result of irradiating said thermal lens; and means for detecting the intensity of at least a portion of said probe light beam after having irradiated said thermal lens during a portion of the dissipation time of said thermal lens, thereby providing an intensity versus time profile related to the thermal diffusivity of said sample material.
Claim 3
Dependent Claim
71 words
The apparatus of claim 1 in which said sample material is substantially transparent to said pulsed laser light beam and said probe light beam, and said focusing lens focal point is chosen to lie between said probe light beam source and said thermal lens, thereby resulting in a defocusing of said probe light beam at said detecting means as a result of said probe light beam passing through said thermal lens.
Claim 4
Dependent Claim
70 words
The apparatus of claim 1 in which said sample material is substantially transparent to said pulsed laser light beam and said probe light beam, and said focusing lens focal point is chosen to lie between said thermal lens and said detecting means, thereby resulting in a further focusing of said probe light beam at said detecting means as a result of said probe light beam passing through said thermal lens.
Claim 5
Dependent Claim
16 words
The apparatus of claim 1 in which said probe light beam source is a cw laser.
Claim 6
Dependent Claim
13 words
The apparatus of claim 1 in which said detecting means is a photodiode.
Claim 7
Dependent Claim
14 words
The apparatus of claim 1 in which said detecting means is a photon counter.
Claim 8
Dependent Claim
17 words
The apparatus of claim 1 in which said detecting means is an area sensitive optical multichannel analyzer.
Claim 9
Dependent Claim
16 words
The apparatus of claim 1 in which said pulsed laser light source is a dye laser.
Claim 10
Dependent Claim
45 words
The apparatus of claim 1 further comprising a filter substantially opaque to said pulsed laser light beam, said filter being located in front of said detecting means so as to intercept any of said pulsed laser light beam which would otherwise irradiate said detecting means.
Claim 11
Dependent Claim
49 words
The apparatus of claim 1 further comprising a processing means whereby successive intensity versus time profiles from said detecting means corresponding to successive pulses from said pulsed laser light source are combined to form a composite intensity versus time profile related to the thermal diffusivity of said sample material.
Claim 12
Independent Claim
209 words
An apparatus for measuring thermal diffusivity of a sample material comprising: a pulsed laser light source for providing a plurality of laser light pulses directed at a sample material, the duration of each pulse being chosen so that each pulse forms a transient thermal lens in said sample material, and the repetition rate of said pulses being chosen so that each thermal lens formed is substantially dissipated before generation of the next pulse; a probe light beam source for providing a probe light beam directed to irradiate said thermal lens during at least a portion of the time said thermal lens is dissipating; a probe light beam focusing lens located between said probe light beam source and said sample material, said focusing lens providing a converging/diverging beam with a focal point at a predetermined location with respect to said thermal lens, thereby resulting in an intensity alteration of said probe light beam as a result of irradiating said thermal lens; and detecting means for providing a plurality of intensity versus time profiles corresponding to a plurality of positions within a portion of said probe light beam after having irradiated said thermal lens, said plurality of intensity versus time profiles being related to the thermal diffusivity of said sample material.
Claim 13
Independent Claim
209 words
An apparatus for measuring thermal diffusivity of a sample material comprising: a pulsed laser light source for providing a plurality of laser light pulses directed at a sample material, the duration of each pulse being chosen so that each pulse forms a transient thermal lens in said sample material, and the repetition rate of said pulses being chosen so that each thermal lens formed is substantially dissipated before generation of the next pulse; a probe light beam source for providing a probe light beam directed to irradiate said thermal lens during at least a portion of the time said thermal lens is dissipating; a probe light beam focusing lens located between said probe light beam source and said sample material, said focusing lens providing a converging/diverging beam with a focal point at a predetermined location with respect to said thermal lens, thereby resulting in an intensity alteration of said probe light beam as a result of irradiating said thermal lens; and detecting means for providing a plurality of intensity versus time profiles corresponding to a plurality of positions within a portion of said probe light beam after having irradiated said thermal lens, said plurality of intensity versus time profiles being related to the thermal diffusivity of said sample material.
Claim 14
Dependent Claim
53 words
The apparatus of claim 11 further comprising a processing means for forming a plurality of composite intensity versus time profiles corresponding to each of said positions, each of said composite profiles being formed from a plurality of intensity versus time profiles formed by a corresponding predetermined plurality of successive laser light beam pulses.
Claim 15
Dependent Claim
16 words
The apparatus of claim 12 in which said probe light beam source is a cw laser.
Claim 16
Independent Claim
176 words
An apparatus for measuring molecular relaxation characteristics of a sample material comprising: a pulsed laser light source for providing a pulsed laser light beam directed to irradiate said sample material whose molecular relaxation characteristics are to be measured, said pulsed laser light beam being chosen to cause formation of a thermal lens in said sample material; a probe light beam source for providing a probe light beam directed to irradiate said thermal lens; a probe light beam focusing lens located between said probe light beam source and said sample material, said focusing lens providing a converging/diverging beam with a focal point at a predetermined location with respect to said thermal lens, thereby resulting in an intensity alteration of said probe light beam as a result of irradiating said thermal lens; and means for detecting the intensity of at least a portion of said probe light beam after having irradiated said thermal lens during the formation of said thermal lens, thereby providing an intensity versus time profile related to the molecular relaxation characteristics of said sample material.
Claim 17
Independent Claim
176 words
An apparatus for measuring molecular relaxation characteristics of a sample material comprising: a pulsed laser light source for providing a pulsed laser light beam directed to irradiate said sample material whose molecular relaxation characteristics are to be measured, said pulsed laser light beam being chosen to cause formation of a thermal lens in said sample material; a probe light beam source for providing a probe light beam directed to irradiate said thermal lens; a probe light beam focusing lens located between said probe light beam source and said sample material, said focusing lens providing a converging/diverging beam with a focal point at a predetermined location with respect to said thermal lens, thereby resulting in an intensity alteration of said probe light beam as a result of irradiating said thermal lens; and means for detecting the intensity of at least a portion of said probe light beam after having irradiated said thermal lens during the formation of said thermal lens, thereby providing an intensity versus time profile related to the molecular relaxation characteristics of said sample material.
Claim 18
Dependent Claim
16 words
The apparatus of claim 14 in which said probe light beam source comprises a cw laser.
Claim 19
Dependent Claim
49 words
The apparatus of claim 14 further comprising a processing means whereby successive intensity versus time profiles from said detecting means corresponding to successive pulses from said pulsed laser light source are combined to form a composite intensity versus time profile related to the molecular relaxation characteristics of said material.
References Cited (Backward Citations)
No citation records indexed.
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